Surface emitting device

ABSTRACT

An edge-emitting type light-emitting device ( 11000, 14000 ) comprises an organic light-emitting layer ( 40 ), a pair of electrode layers ( 30 ) and ( 50 ) for applying an electric field to the organic light-emitting layer ( 40 ), and an optical waveguide which transmits light emitted from the organic light-emitting layer ( 40 ) to the edge. The optical waveguide comprises a core layer ( 20 ) mainly transmitting light, and cladding layers ( 10 ) and ( 60 ) having a refractive index lower than that of the ecore layer ( 20 ). The core layer ( 20 ) may be a layer different from the organic light-emitting layer ( 40 ) or may comprise the organic light-emitting layer. A grating ( 12 ) is formed in the core layer ( 20 ) or in the boundary area between the core layer ( 20 ) and the cladding layer ( 10 ). A light-emitting device ( 31000 ) may comprise an optical fiber section ( 200 ). Another embodiment ( 43000 ) may comprise a defect and a grating having a one-dimensional periodic refractive index distribution and constituting a photonic band gap.

TECHNICAL FIELD

[0001] The present invention relates to a light-emitting deviceutilizing electroluminescence (EL).

BACKGROUND OF ART

[0002] Semiconductor lasers have been used as a light source for anoptical communication system. Semiconductor lasers excel in wavelengthselectivity and are capable of emitting light with a single mode.However, semiconductor lasers require many stages of crystal growth andare difficult to manufacture. Another problem with semiconductor lasersis the limitation to the types of light-emitting materials which can beused. This restricts the wavelength of light which can be emitted bysemiconductor lasers.

[0003] Conventional EL light-emitting devices can emit light with awavelength having a broad spectral width and have been applied todisplays and the like. However, such EL light-emitting devices are unfitfor application to optical communications and the like which requirelight with a narrow spectral width.

DISCLOSURE OF INVENTION

[0004] An object of the present invention is to provide a light-emittingdevice which can emit light with a wavelength having a remarkably narrowspectral width in comparison with conventional EL light-emittingdevices, exhibits directivity, and can be applied to not only displaysbut also optical communications and the like.

[0005] A light-emitting device according to the present inventioncomprises:

[0006] a light-emitting layer being capable of emitting light byelectroluminescence;

[0007] a pair of electrode layers for applying an electric field to thelight-emitting layer; and

[0008] an optical waveguide for transmitting light emitted from thelight-emitting layer,

[0009] wherein a grating is formed in the optical waveguide.

[0010] According to this light-emitting device, electrons and holes areintroduced into the light-emitting layer respectively from the pair ofelectrode layers (cathode and anode). Light is emitted when themolecules return to the ground state from the excited state byrecombination of the electrons and holes in the light-emitting layer.The light emitted from the light-emitting layer is provided withwavelength selectivity and directivity by the grating formed in theoptical waveguide, specifically, a grating with alternating two mediumlayers each of which has a different refractive index arrangedperiodically.

[0011] It is preferable that the grating be a distributed feedback typeor distributed Bragg reflection-type grating. Such a distributedfeedback type or distributed Bragg reflection-type grating causes thelight emitted from the light-emitting layer to resonate. As a result,light having wavelength selectivity, a narrow emission spectral width,and excellent directivity can be obtained. The pitch and depth of thegrating are designed depending on the wavelength of the light to beemitted.

[0012] Light can be emitted with a single mode by providing thedistributed feedback type grating with a λ/4 phase shifted structure ora gain-coupled structure. “λ” used herein indicates the wavelength ofthe light inside the optical waveguide.

[0013] A grating of a distributed feedback type having a λ/4 phaseshifted structure or a gain-coupled structure is a preferableconfiguration common to the light-emitting devices of the presentinvention. It is sufficient for the grating to achieve the abovefunctions. The grating may be formed in any layers constituting theoptical waveguide.

[0014] It is preferable that the light-emitting layer comprises organiclight-emitting materials. Use of organic light-emitting materialsexpands selection of the materials and enables emission of light havingvarious wavelengths in comparison with the case using a semiconductor orinorganic materials.

[0015] The aspects described below from (a) to (d) can be given asexamples of such a light-emitting device.

[0016] (a) In a first aspect of the light-emitting device, the opticalwaveguide comprises a core layer mainly transmitting light, and acladding layer having a refractive index lower than the refractive indexof the core layer; and

[0017] the core layer comprises a layer which is different from thelight-emitting layer.

[0018] A feature of this light-emitting device is that the core layer,which the light transmits mainly, is formed from a layer different fromthe light-emitting layer. The core layer is preferably made frommaterials having a refractive index higher than that of thelight-emitting layer. This refractive index relationship ensuresefficient introduction of the light emitted from the light-emittinglayer into the core layer. The grating may be formed in the core layer.The grating may be formed in the boundary area between the claddinglayer and a layer in contact with the cladding layer such as the corelayer.

[0019] In the case where the light-emitting layer is an organiclight-emitting layer comprising organic materials, the core layer mayserve not only as a light transmitting layer, but also as at least oneof a hole transport layer, electron transport layer, transparentelectrode layer, and the like. The cladding layer is designed to have arefractive index lower than that of the core layer. The cladding layermay serve not only as a layer for light confinement, but also as anelectrode layer, substrate, hole transport layer, electron transportlayer, and the like.

[0020] (b) In a second aspect of the light-emitting device, the opticalwaveguide comprises a core layer mainly transmitting light, and acladding layer having a refractive index lower than the refractive indexof the core layer; and

[0021] the core layer comprises a layer including the light-emittinglayer, and

[0022] the grating is formed in the optical waveguide.

[0023] A feature of this light-emitting device is that thelight-emitting layer is included in the core layer which is the mainlight transmitting layer. The grating may be formed in the core layer.The grating may also be formed in a boundary area between the claddinglayer and a layer in contact with the cladding layer, such as the corelayer. In this light-emitting device, the light-emitting layer may beformed continuously or discontinuously one after another.

[0024] In the case where the light-emitting layer is an organiclight-emitting layer formed by organic light-emitting materials, thecore layer may further comprise at least one of a hole transport layer,an electron transport layer, a transparent electrode layer, and thelike. The cladding layer may be designed to have a refractive indexlower than that of the core layer. The cladding layer may serve not onlyas a layer for light confinement, but also as an electrode layer, asubstrate, an hole transport layer, an electron transport layer, and thelike.

[0025] In the light-emitting device according to this aspect, thegrating may be formed by the light-emitting layer and a layer in contactwith the light-emitting layer. According to the device having such aconfiguration, light emitted from the light-emitting layer resonatesdirectly by the grating in the region including the light-emittinglayer. As a result, light is emitted with a selected wavelength andexcellent directivity.

[0026] (c) The light-emitting device as a third aspect of the presentinvention comprises an optical fiber section formed in one body,

[0027] wherein the optical fiber section comprises a core layer and acladding layer, and

[0028] wherein the optical waveguide is formed continuously with atleast one of the core layer or the cladding layer of the optical fibersection.

[0029] In this light-emitting device, because at least either the corelayer or the cladding layer of the optical fiber section is formed inone body waveguide, light having excellent wavelength selectivity anddirectivity can be emitted from the light-emitting layer in the opticalwaveguide and supplied to the transmission system with high efficiency.

[0030] In this light-emitting device, the light-emitting layer may beincluded in the optical waveguide. The optical waveguide may be eithercontinuous with the core layer of the optical fiber section or formedseparately while being optically connected. Furthermore, it ispreferable that the optical waveguide comprises a core-layer-continuingportion which continues from the core layer of the optical fibersection. In the case where the optical waveguide comprises such a part,light output from the optical waveguide is transmitted to the opticalfiber with high efficiency. Moreover, this highly efficient opticalcombination can be obtained without requiring a delicate opticaladjustment.

[0031] (d) In a fourth aspect of the light-emitting device, the gratinghas a defect and a one-dimensional periodic refractive indexdistribution which constitutes a photonic band gap; and

[0032] the defect is designed so that the energy level caused by thevacancy is within a specific emission spectrum.

[0033] According to this light-emitting device, electrons and holes areintroduced into the light-emitting layer respectively from a pair ofelectrode layers (cathode and anode). Light is emitted when themolecules return to the ground state from the excited state byrecombination of the electrons and holes in the light-emitting layer. Atthis time, light with a wavelength equivalent to the photonic band gapof the grating cannot be transmitted through the grating. Only the lightwith a wavelength equivalent to the energy level caused by the vacancycan be transmitted through the grating. Therefore, light with aremarkably narrow emission spectral width can be obtained with highefficiency by prescribing the width of the energy level caused by thevacancy.

[0034] A special feature of this aspect is in the structure of thegrating. Specifically, the grating has the defect and theone-dimensional periodic refractive index distribution which constitutesthe photonic band gap.

[0035] In this aspect, in order to confine the light and guide it in acertain direction, the grating is preferably formed in the opticalwaveguide comprising areas having either a high refractive index or lowrefractive index. For example, substrates, materials in contact with thegrating or the air layer can function as the cladding layer.

[0036] In the light-emitting device according to this aspect, thelight-emitting layer and the defect of the grating may have thefollowing configuration.

[0037] (1) The light-emitting layer formed in the defect also functionsas the defect.

[0038] (2) The light-emitting layer also functions as at least part ofthe defect and the grating.

[0039] (3) The light-emitting layer is formed in a region different fromthe defect.

[0040] In this aspect, the light-emitting layer is preferably comprisesan organic light-emitting layer formed by organic material. Use of suchan organic light-emitting layer is preferred to the photonic band gapusing semiconductors due to the following reasons. A grating comprisingan organic light-emitting layer which constitutes a photonic band gap isnot affected by the irregular state of the boundary area of thelight-emitting layer and impurities in comparison with the case of usingsemiconductors, whereby excellent characteristics from the photonic bandgap can be obtained. Furthermore, in the case of forming a medium layerfrom an organic light-emitting layer, the manufacture becomes easy and agood periodic structure with a refractive index can be easily obtained,whereby superior characteristics from the photonic band gap can beobtained.

[0041] Some of the materials which can be used for forming each sectionof the light-emitting device according to the present invention will beillustrated below. These materials are only some of the conventionalmaterials. Materials other than these materials can also be used.(Light-emitting layer)

[0042] Materials for the light-emitting layer are selected fromconventional compounds to obtain light with a prescribed wavelength. Anyof organic and inorganic compounds may be used as the materials for thelight-emitting layer. It is preferable to use organic compounds from theviewpoint of a wide variety of compounds and film-formability.

[0043] As examples of such organic compounds, aromatic diaminederivatives (TPD), oxydiazole derivatives (PBD), oxydiazole dimers(OXD-8), distyrarylene derivatives (DSA), beryllium-benzoquinolinolcomplex (Bebq), triphenylamine derivatives (MTDATA), rubrene,quinacridone, triazole derivatives, polyphenylene, polyalkylfluorene,polyalkylthiophene, azomethine zinc complex, polyphyrin zinc complex,benzooxazole zinc complex, and phenanthroline europium complex which aredisclosed in Japanese Patent Application Laid-open No. 10-153967 can begiven.

[0044] Specific examples of materials for the organic light-emittinglayer include compounds disclosed in Japanese Patent ApplicationLaid-open No. 63-70257, No. 63-175860, No. 2-135361, No. 2-135359, No.2-152184, No. 8-248276 and No. 10-153967. These compounds can be usedeither individually or in combinations of two or more.

[0045] As examples of inorganic compounds, ZnS:Mn (red region), ZnS:TbOF(green region), SrS:Cu, SrS:Ag, SrS:Ce (blue region), and the like canbe given. (Optical waveguide)

[0046] The optical waveguide comprises a core layer and a cladding layerhaving a refractive index lower than that of the core layer.Conventional inorganic and organic materials can be used for the corelayer and cladding layer.

[0047] Typical examples of inorganic materials include TiO₂, TiO₂-SiO₂mixture, ZnO, Nb₂O₅, Si₃N₄, Ta₂O₅, HfO₂, and ZrO₂ disclosed in JapanesePatent Application Laid-open No. 5-273427.

[0048] Typical examples of organic materials include variousconventional resins such as thermoplastic resins, thermosetting resins,and photocurable resins. These resins are appropriately selecteddepending on a method of forming layers and the like. For example, inthe case of using a resin which can be cured by energy of at leasteither heat or light, commonly used exposure devices, baking ovens, hotplates, and the like can be utilized.

[0049] As examples of such materials, a UV-curable resin disclosed inJapanese Patent Application No. 10-279439 applied by the applicant ofthe present invention can be given. Acrylic resins are suitable as sucha UV-curable resins. UV-curable acrylic resins having excellenttransparency and capable of being cured in a short period of time can beproduced using various commercially-available resins andphotosensitizers.

[0050] As specific examples of basic components of such UV-curableacrylic resins, prepolymers, oligomers, and monomers can be given.

[0051] Examples of prepolymers or oligomers include acrylates such asepoxy acrylates, urethane acrylates, polyester acrylates, polyetheracrylates, and spiroacetal-type acrylates, methacrylates such as epoxymethacrylates, urethane methacrylates, polyester methacrylates, andpolyether methacrylates, and the like.

[0052] Examples of monomers include monofunctional monomers such as2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-hydroxyethylacrylate, 2-hydroxyethyl methacrylate, N-vinyl-2-pyrrolidone, carbitolacrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate,dicyclopentenyl acrylate, and 1,3-butanediol acrylate, bifunctionalmonomers such as 1,6-hexanediol diacrylate, 1,6-hexanedioldimethacrylate, neopentyl glycol diacrylate, neopentyl glycoldimethacrylate, ethylene glycol diacrylate, polyethylene glycoldiacrylate, and pentaerythritol diacrylate, and polyfunctional monomerssuch as trimethylolpropane triacrylate, trimethylolpropanetrimethacrylate, pentaerythritol triacrylate, and dipentaerythritolhexaacrylate.

[0053] The above examples of inorganic and organic materials areillustrated only in consideration of light confinement. In the casewhere at least one layer among the light-emitting layer, hole transportlayer, electron transport layer, and electrode layer functions as thecore layer or the cladding layer, materials constituting these layerscan be employed as materials for forming the core layer or the claddinglayer constituting the optical waveguide.

Hole Transport Layer

[0054] As materials for the hole transport layer which is optionallyformed, materials conventionally used as hole injection materials forphotoconductive materials or a hole injection layer for organiclight-emitting devices can be selectively used. As the materials for thehole transport layer, any organic or inorganic materials which have afunction of either hole introduction or electron barrier characteristicsare used. Materials disclosed in Japanese Patent Application Laid-openNo. 248276/1996 can be given as specific examples of such materials.

Electron Transport Layer

[0055] Materials for the electron transport layer which is optionallyformed are required to transport electrons introduced from the cathodeto the organic light-emitting layer and can be selected fromconventional materials. Materials disclosed in Japanese PatentApplication Laid-open No. 248276/1996 can be given as specific examplesof such substances.

Electrode Layer

[0056] As the cathode, electron injectable metals, alloys, electricallyconductive compounds with a small work function (for example, 4 eV orless), or mixtures thereof can be used. Materials disclosed in JapanesePatent Application Laid-open No. 248276/1996 can be given as specificexamples of such electrode materials.

[0057] As the anode, metals, alloys, electrically conductive compoundswith a large work function (for example, 4 eV or more), or mixturesthereof can be used. In the case of using optically transparentmaterials as the anode, transparent conductive materials such as CuI,ITO, SnO₂, and ZnO can be used. In the case where transparency is notnecessary, metals such as gold can be used.

[0058] In the present invention, the grating can be formed byconventional methods without specific limitations. Typical examples ofsuch methods are given below.

[0059] 1) Lithographic method

[0060] In this method, a positive or negative resist is irradiated withultraviolet rays, X-rays, or the like. The resist layer is patterned bydevelopment to form a grating. As a patterning technology using apolymethyl methacrylate resist or a novolak resin resist, for example,technologies disclosed in Japanese Patent Applications Laid-open No.6-224115 and No. 7-20637 can be given.

[0061] As a technology of patterning polyimide by photolithography, forexample, technologies disclosed in Japanese Patent ApplicationsLaid-open No. 7-181689 and No. 1-221741 can be given. Furthermore,Japanese Patent Application Laid-open No. 10-59743 discloses atechnology of forming a grating of polymethyl methacrylate or titaniumoxide on a glass substrate utilizing laser ablation.

[0062] 2) Formation of refractive index distribution by irradiation

[0063] In this method, the optical waveguide section of the opticalwaveguide is irradiated with light having a wavelength which produceschanges in the refractive index to periodically form areas havingdifferent refractive indices on the optical waveguide section, therebyforming a grating. As such a method, it is preferable to form a gratingby forming a layer of polymers or polymer precursors and polymerizingpart of the polymer layer by irradiation or the like to periodicallyform areas having a different refractive index. Such a technology isdisclosed in Japanese Patent Applications Laid-open No. 9-311238, No.9-178901, No. 8-15506, No. 5-297202, No. 5-32523, No. 5-39480, No.9-211728, No. 10-26702, No. 10-8300, and No. 2-51101.

[0064] 3) Stamping method

[0065] A grating is formed by, for example, hot stamping using athermoplastic resin (Japanese Patent Application Laid-open No.6-201907), stamping using a UV curable resin (Japanese PatentApplication Laid-open No. 10-279439), or stamping using an electron-beamcurable resin (Japanese Patent Application Laid-open No. 7-235075).

[0066] 4) Etching method

[0067] A thin film is selectively patterned using lithography andetching technologies to form a grating.

[0068] Methods of forming a grating is described above. A gratingconsists of two areas each of which has a different refractive index.Such a grating can be formed by forming such two areas from twomaterials having different refractive indices, by partially modifyingone material to form two areas having different refractive indices, andthe like.

[0069] Each layer of the light-emitting device can be formed by aconventional method. For example, the light-emitting layer is formed bya suitable film-forming method depending on the materials. A vapordeposition method, spin coating method, LB method, ink jet method, andthe like can be given as specific examples.

BRIEF DESCRIPTION OF DRAWINGS

[0070]FIG. 1A is a schematic oblique view of an organic light-emittingdevice according to a first embodiment of the present invention.

[0071]FIG. 1B is a cross-sectional view along the line A-A in FIG. 1A.

[0072]FIG. 2 is a cross-sectional view schematically showing an organiclight-emitting device according to a second embodiment of the presentinvention.

[0073]FIG. 3 is a cross-sectional view schematically showing an organiclight-emitting device according to a third embodiment of the presentinvention.

[0074]FIG. 4 is a cross-sectional view schematically showing an organiclight-emitting device according to a fourth embodiment of the presentinvention.

[0075]FIG. 5 is a cross-sectional view schematically showing an organiclight-emitting device according to a fifth embodiment of the presentinvention.

[0076]FIG. 6 is a cross-sectional view schematically showing an organiclight-emitting device according to a sixth embodiment of the presentinvention.

[0077]FIG. 7 is a cross-sectional view schematically showingmodification of an organic light-emitting device according to a sixthembodiment of the present invention.

[0078]FIG. 8 is a cross-sectional view schematically showing an organiclight-emitting device according to a seventh embodiment of the presentinvention.

[0079]FIG. 9 is a cross-sectional view schematically showing an organiclight-emitting device according to a eighth embodiment of the presentinvention.

[0080]FIG. 10 is a cross-sectional view schematically showing an organiclight-emitting device according to a ninth embodiment of the presentinvention.

[0081]FIG. 11 is a cross-sectional view schematically showing an organiclight-emitting device according to a tenth embodiment of the presentinvention.

[0082]FIG. 12 is a cross-sectional view schematically showing alight-emitting device according to an eleventh embodiment of the presentinvention.

[0083]FIG. 13 is a schematic cross-section viewed along the line B-B inFIG. 12.

[0084]FIG. 14 is a schematic vertical section of a light-emitting deviceaccording to an twelfth embodiment of the present invention.

[0085]FIG. 15 is a schematic cross-section viewed along the line D-D inFIG. 14.

[0086]FIG. 16 is a schematic vertical section of a light-emitting deviceaccording to an thirteenth embodiment of the present invention.

[0087]FIG. 17 is a schematic cross-section viewed along the line F-F inFIG. 16.

[0088]FIG. 18 is a cross-sectional view schematically showing alight-emitting device according to a fourteenth embodiment of thepresent invention.

[0089]FIG. 19 is a schematic cross-section viewed along the line H-H inFIG. 18.

[0090]FIG. 20 is a cross-sectional view schematically showing alight-emitting device according to a fifteenth embodiment of the presentinvention.

[0091]FIG. 21 is a cross-sectional view schematically showing alight-emitting device according to a sixteenth embodiment of the presentinvention.

[0092]FIG. 22 is a cross-sectional view schematically showing alight-emitting device according to a seventeenth embodiment of thepresent invention.

[0093]FIG. 23 is a cross-sectional view schematically showing alight-emitting device according to a eighteenth embodiment of thepresent invention.

[0094]FIG. 24 is a cross-sectional view schematically showing alight-emitting device according to a nineteenth embodiment of thepresent invention.

[0095]FIG. 25 is a cross-sectional view schematically showing alight-emitting device according to a twentieth embodiment of the presentinvention.

[0096]FIG. 26 is a cross-sectional view schematically showing alight-emitting device according to a twenty-first embodiment of thepresent invention.

[0097]FIG. 27 is a cross-sectional view schematically showing alight-emitting device according to a twenty-second embodiment of thepresent invention.

[0098]FIG. 28 is a cross-sectional view schematically showing alight-emitting device according to a twenty-third embodiment of thepresent invention.

[0099]FIG. 29 is a cross-sectional view schematically showing alight-emitting device according to a twenty-fourth embodiment of thepresent invention.

[0100]FIG. 30 is a cross-sectional view schematically showing alight-emitting device according to a twenty-fifth embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0101] (A) Among the embodiments illustrated below, a first to a sixthembodiment relate to an edge-emitting type light-emitting device havinga basic structure provided with a light-emitting layer and an opticalwaveguide having a grating.

[0102] The first to third embodiments illustrate the case where thelight-emitting layer and a core layer which transmits light are formedas different layers.

First Embodiment

[0103]FIG. 1A is a schematic oblique view of an edge-emitting typelight-emitting device 11000 (hereinafter referred to as “organiclight-emitting device”) according to the present embodiment. FIG. 1B isa cross-section viewed along the line A-A in FIG. 1A.

[0104] In the organic light-emitting device 11000, a first claddinglayer 10, core layer 20, anode 30, organic light-emitting layer 40,cathode 50, and second cladding layer 60 are laminated in that order.The refractive indices of the first cladding layer 10 and the secondcladding layer 60 in the organic light-emitting device 11000 aredesigned to be lower than the refractive index of each lighttransmitting layer existing between the first cladding layer 10 and thesecond cladding layer 60.

[0105] The core layer 20 which is the main light transmitting layer isformed along the organic light-emitting layer 40 through the anode 30.The core layer 20 comprises a first layer 20 a and a second layer 20 beach of which has a different refractive index. A grating 22 is formedin the boundary area between the first layer 20 a and the second layer20 b.

[0106] The anode 30 is formed from conductive materials which transmitthe light so that the light emitted from the organic light-emittinglayer 40 is transmitted into the core layer 20. The materials mentionedabove can be used as materials for this transparent electrode. It ispreferable to design the anode 30 and the core layer 20 so that therefractive indices differ from the refractive index of the organiclight-emitting layer 40, whereby the light emitted from the organiclight-emitting layer 40 is efficiently introduced into the core layer20.

[0107] The grating 22 is preferably a distributed feedback type grating.Such a distributed feedback type grating causes light to resonate insidethe optical waveguide, thereby making it possible to obtain lightexhibiting excellent wavelength selectivity and directivity with anarrow emission spectrum width. It is preferable that the grating 22have a λ/4 phase shifted structure or a gain-coupled structure (notshown). Light with a single mode can be emitted more easily by thegrating 22 having a λ/4 phase shifted structure or a gain-coupledstructure.

[0108] A distributed feedback type grating is also preferable in thefollowing second to fifth embodiments. Therefore, this will not bementioned in the description of these embodiments.

[0109] In the organic light-emitting device 11000, a first coating layer100 a with a low reflectance is formed at one edge and a second coatinglayer 110 b with a high reflectance is formed at the other edge. Asthese coating layers, for example, dielectric multi-layered mirrorscommonly used in semiconductor DFB lasers can be used.

[0110] It is also preferable that a light-emitting device have suchdielectric multi-layered mirrors in the following second to sixthembodiments. Therefore, this will not be mentioned in the description ofthese embodiments.

[0111] The action and the effect of the organic light-emitting device11000 will be described below.

[0112] Electrons and holes are injected into the organic light-emittinglayer 40 respectively from the cathode 50 and the anode 30 by applying aprescribed voltage to both the anode 30 and the cathode 50. Excitons areformed in the organic light-emitting layer 40 by recombination of theelectrons and holes. Light such as fluorescent light and phosphorescentlight is emitted when these excitons are deactivated.

[0113] The light emitted from the organic light-emitting layer 40 ispartially reflected by the cathode 50 or the second cladding layer 60.Part of the light is directly introduced into the core layer 20 throughthe anode 30 which consists of a transparent conductive layer. The lightintroduced into the core layer 20 is transmitted inside the core layer20 toward the edge thereof by the distributed feedback type transmissionbecause of the grating 22, and is emitted from the first low reflectancecoating layer 100 a.

[0114] The light is emitted through distributed feedback in the corelayer 20 by the grating 22. Because of this, the emitted light haswavelength selectivity, a narrower emission spectrum width, andexcellent directivity. Furthermore, light with a single mode can beobtained more easily by the grating 22 having a λ/4 phase shiftedstructure or a gain-coupled structure. “λ” used herein indicates thewavelength of the light inside the optical waveguide. The effect of thedistributed feedback type grating is the same as in the following secondto fifth embodiments. Therefore, this will not be mentioned in thedescription of these embodiments.

[0115] The second cladding layer 60 is formed outside the cathode 50 inthe example shown in the figure. In the case where the cathode 50 canfully reflect the light emitted from the organic light-emitting layer40, the second cladding layer 60 may be left out. This also applies toother embodiments having a similar structure.

[0116] In the example shown in the figure, the core layer 20 is formedbetween the first cladding layer 10 and the anode 30. The core layer 20may be formed between the cathode 50 and the second cladding layer 60.For example, in the case where the cathode 50 is thin, the cathode 50can transmit light emitted from the light-emitting layer 40. In thiscase, light with excellent wavelength selectivity and directivity can beemitted from the low reflectance first coating layer 100 a by formingthe core layer 20 having the grating 22 outside the cathode 50 in thesame manner as in the above-described case. This modification alsoapplies to other embodiments having a similar structure.

[0117] Either the first layer 20 a or second layer 20 b constituting thecore layer 20 may be a gaseous layer such as air. In the case of forminga grating using such a gaseous layer, the difference in the refractiveindices of the two medium layers constituting the grating can be widerwhile using conventional materials used for light-emitting devices.Therefore, a good grating which is efficient for a desired lightwavelength can be obtained.

[0118] As a method for manufacturing the grating or organiclight-emitting layer in the organic light-emitting device 11000 andmaterials constituting each layer, the methods and materials describedabove can be appropriately used. For example, in the formation of thegrating 22 in the core layer 20, a comparatively simple stamping methodand the like can be preferably used. These methods and materials alsoapply to the following embodiments.

Second Embodiment

[0119]FIG. 2 is a cross-sectional view schematically showing an organiclight-emitting device 12000 according to the present embodiment. Thisorganic light-emitting device 12000 forms the grating in the areadifferent from the organic light-emitting device 11000 according to thefirst embodiment.

[0120] In the organic light-emitting device 12000, a first claddinglayer 10, core layer 20, anode 30, organic light-emitting layer 40,cathode 50, and second cladding layer 60 are laminated in that order.The refractive indices of the first cladding layer 10 and the secondcladding layer 60 in the organic light-emitting device 12000 aredesigned to be lower than the refractive index of each lighttransmitting layer existing between the first cladding layer 10 and thesecond cladding layer 60.

[0121] The light-transmitting core layer 20 is formed along the organiclight-emitting layer 40 through the anode 30. A grating 12 is formed inthe boundary area between the core layer 20 and the first cladding layer10.

[0122] The anode 30 is formed from conductive materials which transmitlight so that the light emitted from the organic light-emitting layer 40is introduced into the core layer 20. The materials mentioned above canbe used as materials for this transparent electrode. The anode 30 andthe core layer 20 are preferably designed so that the refractive indicesdiffer from the refractive index of the organic light-emitting layer 40in order to efficiently introduce the light emitted from the organiclight-emitting layer 40 into the core layer 20.

[0123] The action and the effect of the organic light-emitting device12000 will be described below.

[0124] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 by applying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is partially reflected by the cathode 50 or the second cladding layer60. Part of the light is directly introduced into the core layer 20through the anode 30 which consists of a transparent conductive layer.

Third Embodiment

[0125]FIG. 3 is a cross-sectional view schematically showing an organiclight-emitting device 13000 according to a third embodiment. The organiclight-emitting device 13000 differs from the organic light-emittingdevice 11000 of the first embodiment in having a hole transport layerand an electron transport layer.

[0126] In the organic light-emitting device 13000, a first claddinglayer 10, anode 30, hole transport layer 70, organic light-emittinglayer 40, electron transport layer 80, cathode 50, and second claddinglayer 60 are laminated in that order. The refractive indices of thefirst cladding layer 10 and the second cladding layer 60 in the organiclight-emitting device 13000 are designed to be lower than the refractiveindex of each light transmitting layer existing between the firstcladding layer 10 and the second cladding layer 60.

[0127] The feature of this embodiment is that the hole transport layer70 also functions as the core layer 20 in the first embodiment.Specifically, the hole transport layer 70 which functions as a corelayer comprises a first layer 70 a and a second layer 70 b each having adifferent refractive index. A grating 72 is formed in the boundary areabetween the first layer 70 a and the second layer 70 b in the directionof light transmission.

[0128] It is preferable to design the hole transport layer 70 so thatthese refractive indices differ from the refractive index of the organiclight-emitting layer 40 in order to efficiently introduce the lightemitted from the organic light-emitting layer 40 into the hole transportlayer 70.

[0129] The action and the effect of the organic light-emitting device13000 will be described below.

[0130] Electrons are injected from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is partially reflected by the cathode 50 or the second cladding layer60. Part of the light is directly introduced into the hole transportlayer 70. The light introduced into the hole transport layer 70 istransmitted inside a waveguide layer 74 toward the edge thereof bydistributed feedback type transmission due to the grating 72. The lightis emitted from a first coating layer with a low reflectance (notshown).

[0131] The embodiment illustrates the case of forming the grating 72 inthe hole transport layer 70. The grating may be formed in the electrontransport layer 80 instead of the hole transport layer 70. It isunnecessary to form both the hole transport layer and the electrontransport layer. Either of these transport layers may be enough. Thisalso applies to other embodiments.

[0132] The grating 72 is formed inside the hole transport layer 70 inthis embodiment. A grating may be formed by the hole transport layer 70and the anode 30 made of ITO and the like which is not a metalelectrode.

[0133] The following fourth and fifth embodiments illustrate the casewhere the core layer comprises the organic light-emitting layer.

Fourth Embodiment

[0134]FIG. 4 is a cross-sectional view schematically showing an organiclight-emitting device 14000 according to the present embodiment.

[0135] A feature of this organic light-emitting device 14000 is that anorganic light-emitting layer 40 is sandwiched between a hole transportlayer 70 and a electron transport layer 80 and a grating is formed inthe organic light-emitting layer 40.

[0136] In the organic light-emitting device 14000, a first claddinglayer 10, anode 30, hole transport layer 70, organic light-emittinglayer 40, electron transport layer 80, cathode 50, and second claddinglayer 60 are laminated in that order. The refractive indices of thefirst cladding layer 10 and the second cladding layer 60 in the organiclight-emitting device 14000 are designed to be lower than the refractiveindex of each light transmitting layer existing between the firstcladding layer 10 and the second cladding layer 60.

[0137] In this embodiment, the organic light-emitting layer 40 and theelectron transport layer 80 also function as a light-transmitting corelayer. A grating 42 is formed in the boundary area between the organiclight-emitting layer 40 and the electron transport layer 80. Therefore,the refractive indices of the organic light-emitting layer 40 and theelectron transport layer 80 are designed to be different.

[0138] The action and the effect of the organic light-emitting device14000 will be described below.

[0139] Electrons are injected from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is transmitted inside the organic light-emitting layer 40 and theelectron transport layer 80 toward the edges thereof by distributedfeedback type transmission due to the grating 42. The light is emittedfrom a first coating layer with a low reflectance (not shown).

[0140] According to this organic light-emitting device 14000, becausethe light emitted from the organic light-emitting layer 40 istransmitted inside the organic light-emitting layer 40, efficient lightemission is ensured by appropriately selecting the materials for theorganic light-emitting layer 40.

[0141] The grating 42 is formed by the organic light-emitting layer 40and the electron transport layer 80 in the organic light-emitting device14000 of this embodiment. In the case of using a nonmetallic substancesuch as diamond as the material for the cathode 50, the grating may beformed by the cathode 50 and the electron transport layer 80. If theelectron transport layer 80 is not formed, the grating may be formed bythe cathode 50 and the organic light-emitting layer 40.

Fifth Embodiment

[0142]FIG. 5 is a cross-sectional view schematically showing an organiclight-emitting device 15000 according to the present embodiment. In thisorganic light-emitting device 15000, the organic light-emitting layerconstitutes the grating as in the fourth embodiment. However, thisorganic light-emitting device does not have a second cladding layer.

[0143] In the organic light-emitting device 15000, a cladding layer 10,anode 30, hole transport layer 70, organic light-emitting layer 40, andcathode 50 are laminated in that order. A grating 72 is formed in theboundary area between the organic light-emitting layer 40 and the holetransport layer 70. Therefore, the refractive indices of the organiclight-emitting layer 40 and the hole transport layer 70 are designed tobe different.

[0144] In this organic light-emitting device 15000, the organiclight-emitting layer 40 and hole transport layer 70 function as a corelayer which transmits light.

[0145] The action and the effect of the organic light-emitting device15000 will be described below.

[0146] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of the electrons and holes.Light such as fluorescent light and phosphorescent light is emitted whenthese excitons are deactivated. The light emitted from the organiclight-emitting layer 40 is transmitted inside the organic light-emittinglayer 40 and the hole transport layer 70 toward the edges thereof bydistributed feedback type transmission due to the grating 72. The lightis emitted from a first coating layer with a low reflectance (notshown).

[0147] According to this organic light-emitting device 15000, becausepart of the organic light-emitting layer 40 constitutes the grating 72,light is emitted with high efficiency by appropriately selecting thematerials for the organic light-emitting layer 40.

Sixth Embodiment

[0148]FIG. 6 is a cross-sectional view schematically showing an organiclight-emitting device 16000 according to the present embodiment. Thisorganic light-emitting device 16000 differs from the above-describedorganic light-emitting devices in having a distributed Braggreflection-type grating.

[0149] In the organic light-emitting device 16000, a cladding layer 10,anode 30, hole transport layer 70, organic light-emitting layer 40, andcathode 50 are laminated in that order. The refractive index of thecladding layer 10 in the organic light-emitting device 16000 is designedto be lower than the refractive index of each light-transmitting layer.

[0150] A grating 72 formed in the boundary area between the holetransport layer 70 and an air layer 90 constitutes a distributedBragg-type grating having an air gap. A concavity 42 is formed in partof the surface of the hole transport layer 70. The organiclight-emitting layer 40 is formed in the concavity 42. The cathode 50 isformed on the organic light-emitting layer 40. In the organiclight-emitting device 16000, the hole transport layer 70 and the airlayer 90 function as a light-transmitting core layer.

[0151] The distributed Bragg-type grating 72 causes light to resonate,whereby light with excellent wavelength selectivity and directivity canbe obtained.

[0152] The action and the effect of the organic light-emitting device16000 will be described below.

[0153] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of the electrons and holes.Light such as fluorescent light and phosphorescent light is emitted whenthese excitons are deactivated.

[0154] Because this embodiment has the distributed Bragg reflection-typegrating 72, light emitted from the organic light-emitting layer 40 isreflected by the grating at both sides of the organic light-emittinglayer 40 and resonates. Therefore, the light emitted from the organiclight-emitting layer 40 resonates more efficiently and is transmittedinside the hole transport layer 70 and the air layer 90 toward the edgesthereof. The light is emitted from a first coating layer with a lowreflectance (not shown). Because the light is emitted after resonatingby the distributed Bragg reflection-type grating 72, the light not onlyhas excellent wavelength selectivity and directivity but also is emittedwith high efficiency.

[0155] The grating 72 is formed in the hole transport layer 70 in theexample shown in the figure. The grating may be formed in an electrontransport layer which is formed instead of the hole transport layer. Acore layer may be formed from materials with small light absorptioninstead of forming the hole transport layer or electron transport layer.One of layers constituting gratings, which comprise air in the exampleshown in the figure, may be a layer formed from other materials.Furthermore, at least either the hole transport layer or the electrontransport layer may be embedded into the concavity 42 in addition to theorganic light-emitting layer 40.

[0156] The grating is formed by the hole transport layer 70 on the anode30 and the air layer 90 in the organic light-emitting device 16000 shownin FIG. 6. For example, a distributed Bragg reflection-type grating 22shown in FIG. 7 may be formed using two medium layers each of which hasa different refractive index (a core layer 20 and an air layer 90 inFIG. 7) below the anode 30.

[0157] (B) The following seventh to tenth embodiments illustrateexamples in which a light-emitting layer constitutes a medium layer of agrating and the light-emitting layer is discontinuous.

Seventh Embodiment

[0158]FIG. 8 is a cross-sectional view schematically showing anedge-emitting type organic light-emitting device 21000 according to thepresent embodiment.

[0159] In the organic light-emitting device 21000, a first claddinglayer 10, anode 30, hole transport layer 70, organic light-emittinglayer 40, cathode 50, and second cladding layer 60 are laminated in thatorder. The refractive indices of the first cladding layer 10 and thesecond cladding layer 60 in the organic light-emitting device 21000 aredesigned to be lower than the refractive index of each lighttransmitting layer existing between the first cladding layer 10 and thesecond cladding layer 60. The organic light-emitting layer 40 issandwiched between the hole transport layer 70 and the cathode 50.

[0160] In this embodiment, at least the organic light-emitting layer 40and the hole transport layer 70 also function as a light-transmittingcore layer. A grating 110 is formed by the organic light-emitting layer40 and the hole transport layer 70. Therefore, the refractive indices ofthe organic light-emitting layer 40 and the hole transport layer 70 aredesigned to be different. Specifically, the grating 110 is formed byforming concavities 72 with a prescribed pitch and depth in the upperportion of the hole transport layer 70 and filling the organiclight-emitting layer 40 therein. Therefore, the organic light-emittinglayers 40 are separated at a prescribed pitch.

[0161] The grating 110 is preferably a distributed feedback typegrating. Light having excellent wavelength selectivity, a narrowemission spectrum width, and superior directivity can be obtained byforming such a distributed feedback type grating. It is preferable thatthe grating 110 have a λ/4 phase shifted structure or a gain-coupledstructure (not shown). Such a λ/4 phase shifted structure or again-coupled structure ensures that the light is emitted with a singlemode.

[0162] A distributed feedback type grating is also preferable in thefollowing eighth to tenth embodiments. Therefore, this will not befurther mentioned in the description of these embodiments.

[0163] In the organic light-emitting device 21000, a first coating layerwith a low reflectance is formed at one edge and a second coating layerwith a high reflectance is formed at the other edge (not shown). Asthese coating layers, for example, dielectric multi-layered mirrorscommonly used in semiconductor DFB lasers can be used.

[0164] It is also preferable that a light-emitting device have suchdielectric multi-layered mirrors in the following eighth to tenthembodiments. Therefore, this will not be further mentioned in thedescription of these embodiments.

[0165] Although not shown in the figure showing the organiclight-emitting device 21000, it is preferable to form an insulatinglayer on the surface of the convexities of the hole transport layer 70,in other words, between the hole transport layer 70 and the cathode 50in the area where the light-emitting layers 40 are not formed. Thecurrent injection efficiency into the light-emitting layer 40 can beimproved by forming such an insulating layer.

[0166] The action and the effect of the organic light-emitting device21000 will be described below.

[0167] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of the electrons and holes.Light such as fluorescent light and phosphorescent light is emitted whenthese excitons are deactivated. The light emitted from the organiclight-emitting layer 40 is transmitted inside a core layer toward theedge thereof by distributed feedback type transmission due to thegrating 110. The light is emitted from the first coating layer with alow reflectance.

[0168] The light is emitted through distributed feedback by the grating110. Because of this, the emitted light has wavelength selectivity, anarrower emission spectrum width, and excellent directivity.Furthermore, light with a single mode can be obtained more easily by thegrating 110 having a λ/4 phase shifted structure or a gain-coupledstructure. “λ” used herein indicates the wavelength of the light insidethe optical waveguide. This also applies to the following eighth totenth embodiments and will not be mentioned in the description of theseembodiments.

[0169] According to this organic light-emitting device 21000, becausethe light emitted from the organic light-emitting layer 40 istransmitted inside the organic light-emitting layer 40, efficient lightemission is ensured by appropriately selecting the materials for theorganic light-emitting layer 40.

Eighth Embodiment

[0170]FIG. 9 is a cross-sectional view schematically showing anedge-emitting type organic light-emitting device 22000 according to thepresent embodiment.

[0171] In the organic light-emitting device 22000, a first claddinglayer 10, anode 30, hole transport layer 70, organic light-emittinglayer 40, electron transport layer 80, cathode 50, and second claddinglayer 60 are laminated in that order. The refractive indices of thefirst cladding layer 10 and the second cladding layer 60 in the organiclight-emitting device 22000 are designed to be lower than the refractiveindex of each light transmitting layer existing between the firstcladding layer 10 and the second cladding layer 60. The organiclight-emitting layer 40 is sandwiched between the hole transport layer70 and the cathode 50.

[0172] In this embodiment, at least the organic light-emitting layer 40and the electron transport layer 80 also function as alight-transmitting core layer. A grating 110 is formed by the organiclight-emitting layer 40 and the electron transport layer 80. Therefore,the refractive indices of the organic light-emitting layer 40 and theelectron transport layer 80 are designed to be different. Specifically,the grating 110 is formed by forming the organic light-emitting layers40 with a prescribed pitch and height on the hole transport layer 70 andfilling part of the electron transport layer 80 into the concavitiesformed between the adjacent organic light-emitting layers 40.

[0173] Although not shown in the figure illustrating the organiclight-emitting device 22000, it is preferable to form an insulatinglayer between the hole transport layer 70 and the electron transportlayer 80 in the area where the light-emitting layers 40 are not formed.The efficiency of current injection into the light-emitting layer 40 canbe improved by forming such an insulating layer.

[0174] The action and the effect of the organic light-emitting device22000 will be described below.

[0175] Electrons are injected from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is transmitted inside a core layer toward the edge thereof bydistributed feedback type transmission due to the grating 110. The lightis emitted from the first coating layer with a low reflectance (notshown).

[0176] According to this organic light-emitting device 22000, becausethe light emitted from the organic light-emitting layer 40 istransmitted inside the organic light-emitting layer 40, efficient lightemission is ensured by appropriately selecting the materials for theorganic light-emitting layer 40.

Ninth Embodiment

[0177]FIG. 10 is a cross-sectional view schematically showing anedge-emitting type organic light-emitting device 23000 according to thepresent embodiment.

[0178] In the organic light-emitting device 23000, a first claddinglayer 10, anode 30, organic light-emitting layer 40, electron transportlayer 80, cathode 50, and second cladding layer 60 are laminated in thatorder. The refractive indices of the first cladding layer 10 and thesecond cladding layer 60 in the organic light-emitting device 23000 aredesigned to be lower than the refractive index of each lighttransmitting layer existing between the first cladding layer 10 and thesecond cladding layer 60. The organic light-emitting layer 40 isinterposed between the anode 30 and the electron transport layer 80. Theorganic light-emitting layer 40 constitutes the grating 110.

[0179] In this embodiment, at least the anode 30, organic light-emittinglayer 40, and electron transport layer 80 also function as alight-transmitting core layer. The grating 110 is formed by the organiclight-emitting layer 40 and anode 30. Therefore, the refractive indicesof the organic light-emitting layer 40 and the electron transport layer80 are designed to be different and a transparent conductive layerconstitutes the anode 30. Specifically, the grating 110 is formed byforming concavities 32 with a prescribed pitch and depth in the upperportion of the anode 30 and filling the organic light-emitting layer 40therein. Therefore, the organic light-emitting layers 40 are separate ata prescribed pitch.

[0180] The action and the effect of the organic light-emitting device23000 will be described below.

[0181] Electrons are injected from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 into theorganic light-emitting layer 40 by applying a prescribed voltage to theanode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of the electrons and holes.Light such as fluorescent light and phosphorescent light is emitted whenthese excitons are deactivated. The light emitted from the organiclight-emitting layer 40 is transmitted inside a core layer toward theedge thereof by distributed feedback type transmission due to thegrating 110. The light is emitted from the first coating layer with alow reflectance (not shown).

[0182] According to this organic light-emitting device 23000, becausethe light emitted from the organic light-emitting layer 40 istransmitted inside the organic light-emitting layer 40, efficient lightemission is ensured by appropriately selecting the materials for theorganic light-emitting layer 40.

Tenth Embodiment

[0183]FIG. 11 is a cross-sectional view schematically showing anedge-emitting type organic light-emitting device 24000 according to thepresent embodiment.

[0184] In the organic light-emitting device 24000, a first claddinglayer 10, anode 30, hole transport layer 70, The grating 110 formed byan organic light-emitting layer 40 and medium layer 90, cathode 50, andsecond cladding layer 60 are laminated in that order. The refractiveindices of the first cladding layer 10 and the second cladding layer 60in the organic light-emitting device 24000 are designed to be lower thanthe refractive index of each light transmitting layer existing betweenthe first cladding layer 10 and the second cladding layer 60. Theorganic light-emitting layer 40 is interposed between the hole transportlayer 70 and the cathode 50.

[0185] In this embodiment, at least the grating 110 comprising theorganic light-emitting layer 40 and the electron transport layer 80 alsofunction as a light-transmitting core layer. A grating 110 is formed bythe organic light-emitting layer 40 and the medium layer 90. Therefore,the refractive indices of the organic light-emitting layer 40 and themedium layer 90 are designed to be different. Specifically, the grating110 is formed by forming the medium layer 90 with a prescribed pitch andheight on the hole transport layer 70 and filling the organiclight-emitting layers 40 between the medium layers 90. Therefore, theorganic light-emitting layers 40 are separated at a prescribed pitch.The organic light-emitting layers 40 may be formed prior to the mediumlayers 90. The medium layers 90 are preferably formed from organic orinorganic insulation materials. The current injection efficiency intothe light-emitting layer 40 can be improved if the medium layers 90 haveinsulating properties.

[0186] The action and the effect of the organic light-emitting device24000 will be described below.

[0187] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of the electrons and holes.Light such as fluorescent light and phosphorescent light is emitted whenthese excitons are deactivated. The light emitted from the organiclight-emitting layer 40 is transmitted inside a core layer toward theedge thereof by distributed feedback type transmission due to thegrating 110. The light is emitted from the first coating layer with alow reflectance (not shown).

[0188] According to this organic light-emitting device 24000, becausethe light emitted from the organic light-emitting layer 40 istransmitted inside the organic light-emitting layer 40, efficient lightemission is ensured by appropriately selecting the materials for theorganic light-emitting layer 40.

[0189] The above seventh to tenth embodiments illustrate examples usingthe organic light-emitting layer as a medium for a grating. The presentinvention is not limited to these embodiments and various embodimentscan be employed. For example, a grating may consist of an organiclight-emitting layer and other layers and such other layers may be agaseous layer such as air other than the layers described for the aboveembodiments. In the case of forming a grating with an air gap structureusing such a gaseous layer, the difference in the refractive indices ofthe two medium layers which constitute the grating can be wider usingcommon materials employed for the light-emitting device, therefore, agood grating which is efficient for a desired light wavelength.

[0190] (C) The following eleventh to fourteenth embodiments illustrateexamples of an optical fiber integrated light-emitting device comprisingan organic light-emitting layer, optical waveguide having a grating, andoptical fiber section. In these embodiments, a section having alight-emitting function equivalent to the light-emitting devicedescribed above is referred to as an “EL element section”.

Eleventh Embodiment

[0191]FIG. 12 is a schematic vertical section of an organiclight-emitting device 31000 according to the present embodiment. FIG. 13is a schematic cross-section viewed along the line B-B in FIG. 12.

[0192] The light-emitting device 31000 comprises an optical fibersection 200 and an EL element section 100 formed at the end of theoptical fiber section 200.

[0193] The optical fiber section 200 comprises a core layer 90 and acladding layer 95 surrounding the core layer 90.

[0194] Each layer in the EL element section 100 is formed in almostconcentric circles as shown in cross-section in FIG. 13. An EL corelayer 20, anode 30, organic light-emitting layer 40, cathode 50, and ELcladding layer 60 are laminated in that order from the center. Therefractive index of the EL cladding layer 60 in the light-emittingdevice 31000 is designed to be lower than the refractive index of eachlight transmitting layer encircled by the EL cladding layer 60.

[0195] The light-transmitting EL core layer 20 formed along the insideof the anode 30 is a core-layer-continuing portion 92 which continuesfrom the core layer 90 of the optical fiber section 200. In the EL corelayer 20, a first layer 20 a and a second layer 20 b each of which has adifferent refractive index continue alternately in the direction of thelength to form a grating 22. The light-emitting device 31000 comprisesthe EL core layer 20 which comprises the core-layer-continuing portion92 which continues from the core layer 90 of the optical fiber section200, whereby the light output from the EL core layer 20 is transmittedto the optical fiber with high efficiency. Moreover, this highlyefficient combination is obtained without performing a delicate opticaladjustment.

[0196] The anode 30 is formed from conductive materials which transmitlight so that the light emitted from the organic light-emitting layer 40is introduced into the EL core layer 20. The materials mentioned abovecan be used as materials for this transparent electrode. It ispreferable to design the anode 30 and the EL core layer 20 so that therefractive indices differ from the refractive index of the organiclight-emitting layer 40, whereby the light emitted from the organiclight-emitting layer 40 is efficiently introduced into the EL core layer20. In particular, the refractive index of the EL core layer 20 ispreferably designed to be higher than the refractive index of theorganic light-emitting layer 40.

[0197] The grating 22 is preferably a distributed feedback type grating.Such a distributed feedback type grating causes light to resonate,thereby making it possible to obtain excellent light exhibitingwavelength selectivity and directivity with a narrow emission spectrumwidth. It is preferable that the grating 22 have a λ/4 phase shiftedstructure or a gain-coupled structure (not shown). Such a λ/4 phaseshifted structure or a gain-coupled structure ensures that the light isemitted with a single mode.

[0198] It is also preferable to form a distributed feedback type gratingas in the following twelfth to fourteenth embodiments. Therefore, thiswill not be further mentioned in the description of these embodiments.

[0199] In the light-emitting device 31000, a coating layer 14 with ahigh reflectance is formed at one end. As the coating layer 14, forexample, dielectric multi-layered mirrors commonly used in semiconductorDFB lasers can be used.

[0200] It is also preferable to provide such a dielectric multi-layeredmirror as in the following twelfth to fourteenth embodiments. Therefore,this will not be further mentioned in the description of theseembodiments.

[0201] The action and the effect of the light-emitting device 31000 willbe described below.

[0202] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 by applying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated.

[0203] The light emitted from the organic light-emitting layer 40 ispartially reflected by the cathode 50 or the EL cladding layer 60. Partof the light is directly introduced into the EL core layer 20 throughthe anode 30 made of a transparent conductive layer. The lightintroduced into the EL core layer 20 is transmitted inside the EL corelayer 20 by distributed feedback type transmission due to the grating 22and is emitted to the core layer 90 of the optical fiber section 200.The light is emitted through distributed feedback in the EL core layer20 by the grating 22. Because of this, the emitted light has wavelengthselectivity, a narrower emission spectrum width, and excellentdirectivity.

[0204] Furthermore, light with a single mode can be obtained more easilyby the grating 22 having a λ/4 phase shifted structure or a gain-coupledstructure. “λ” used herein indicates the wavelength of the light insidethe optical waveguide. This also applies to the following twelfth tofourteenth embodiments and will not be further mentioned in thedescription of these embodiments.

[0205] Because the EL core layer 20 comprises the core-layer-continuingportion 92 which continues from the core layer 90 of the optical fibersection 200, the light output from the EL core layer 20 is introducedinto the optical fiber section 200 with high efficiency. Moreover, thereis no need to perform a delicate optical adjustment.

[0206] The EL cladding layer 60 is formed outside the cathode 50 in theexample shown in the figure. In the case where the cathode 50 can fullyreflect the light emitted from the organic light-emitting layer 40, theEL cladding layer 60 may be omitted. This also applies to the followingtwelfth to fourteenth embodiments.

[0207] The anode 30 is formed so as to be in contact with the EL corelayer 20 in the example shown in the figure. The cathode 50 may beformed so as to be in contact with the EL core layer and the anode 30may be formed outside the organic light-emitting layer 40. For example,in the case where the cathode 50 is thin, light emitted from thelight-emitting layer 40 can penetrate the cathode 50. In this case,light with excellent wavelength selectivity and directivity can beemitted to the core layer 90 of the optical fiber section 200 in thesame manner as in the above cases by forming the EL core layer 20 havingthe grating 22 inside the cathode 50. This modification also applies tothe following twelfth to fourteenth embodiments.

[0208] Instead of forming the anode 30 and cathode 50 to be in contactwith the organic light-emitting layer 40, a hole transport layer may beformed between the anode 30 and the organic light-emitting layer 40 oran electron transport layer may be formed between the cathode 50 and theorganic light-emitting layer 40.

[0209] In order to obtain a good external connection, it is preferableto expose the peripheries, that is, the curved surfaces of the anode 30and the cathode 50 to secure an electrical connection in the wide area.

[0210] As a method of manufacturing a grating 22 or organiclight-emitting layer 40 of the light-emitting device 31000 and materialsconstituting each layer, the methods and materials described above canbe appropriately used. For example, in the formation of the grating 22in the EL core layer 20, a method of forming a refractive indexdistribution by irradiation and the like can be preferably used. Thesemethods and materials also apply to the following twelfth to fourteenthembodiments.

Twelfth Embodiment

[0211]FIG. 14 is a schematic vertical section of a light-emitting device32000 according to the present embodiment. FIG. 15 is a schematiccross-section viewed along the line D-D in FIG. 14.

[0212] In the light-emitting device 32000, the EL element section is notformed in concentric circles like the eleventh embodiment as shown inthese figures. The feature of the light-emitting device 32000 is asfollows. In the light-emitting device 32000 according to thisembodiment, almost half of a core-layer-continuing portion 92 and acladding-layer-continuing portion 97 which continue respectively from acore layer 90 and a cladding layer 95 of an optical fiber section 200 isremoved horizontally. An anode 30, organic light-emitting layer 40,cathode 50, and EL cladding layer 60 are laminated almost flat on thesection. Other features are as same as in the eleventh embodiment anddescription thereof is omitted. Corresponding sections in each figureare indicated by the same symbols as in the eleventh embodiment.

[0213] As shown in cross-sectional FIG. 15, almost half of thecore-layer-continuing portion 92 and the cladding-layer-continuingportion 97 which continue respectively from the core layer 90 and thecladding layer 95 of the optical fiber section 200 is removedhorizontally in the EL element section 300. The anode 30, organiclight-emitting layer 40, cathode 50, and EL cladding layer 60 arelaminated almost flat on the section. The anode 30 is formed flat to becontinuously in contact with the core-layer-continuing portion 92. Theorganic light-emitting layer 40 is formed flat to be in contact with theother side of the anode 30. The cathode 50 is formed flat to be incontact with the organic light-emitting layer 40. The EL cladding layer60 is formed to enclose the anode 30, organic light-emitting layer 40,and cathode 50 in the directions of the lengths. The EL cladding layer60 is joined with the cladding-layer-continuing portion 97. Therefractive index of the EL cladding layer 60 in the light-emittingdevice 32000 is designed to be lower than the refractive index of eachlight transmitting layer enclosed by the EL cladding layer 60.

[0214] The EL core layer 20 is formed along the bottom of the anode 30and comprises the core-layer-continuing portion 92 which continues fromthe core layer 90 of the optical fiber section 200. In the EL core layer20, a first layer 20 a and a second layer 20 b, each of which has adifferent refractive index, continue alternately in the direction of thelength to form a grating 22. The light-emitting device 32000 comprisesthe EL core layer 20 which comprises the core-layer-continuing portion92 which continues from the core layer 90 of the optical fiber section200, whereby the light output from the EL core layer 20 is transmittedto the optical fiber with high efficiency. Moreover, this highlyefficient combination is obtained without performing a delicate opticaladjustment.

[0215] Either the first layer 20 a or second layer 20 b whichconstitutes the EL core layer 20 may be a gaseous layer such as air. Inthe case of forming the grating 22 by such a gaseous layer, the grating22 having a large difference in the refractive index between the layers20 a and 20 b can be easily formed.

[0216] In the EL element section 300 according to this embodiment, theanode 30, organic light-emitting layer 40, and cathode 50 are formedcorresponding to the width of the EL core layer 20 as shown in FIG. 15.For example, the anode 30, organic light-emitting layer 40, and cathode50 may all be formed over the EL core layer 20 and thecladding-layer-continuing portion 97 on the section shown in FIG. 15.

Thirteenth Embodiment

[0217]FIG. 16 is a schematic vertical section of a light-emitting device33000 according to the present embodiment. FIG. 17 is a schematiccross-section viewed along the line F-F in FIG. 16.

[0218] This light-emitting device 33000 differs from the light-emittingdevice 31000 according to the eleventh embodiment in that the EL corelayer 20 comprises the core-layer-continuing portion 92 and the anode30. Other features are as same as in the eleventh embodiment anddescription thereof is omitted. Corresponding sections in each figureare indicated by the same symbols as in the eleventh embodiment.

[0219] The light-transmitting EL core layer 20 is formed by the anode 30and the core-layer-continuing portion 92. In the EL core layer 20, agrating 32 is formed in the boundary area between the anode 30 and thecore-layer-continuing portion 92 where the first layer 20 a (anode 30)and the second layer 20 b (core-layer-continuing portion 92) continuealternately in the direction of the length. The light-emitting device33000 comprises the EL core layer 20 which comprises thecore-layer-continuing portion 92 which continues from the core layer 90of the optical fiber section 200, whereby the light output from the ELcore layer 20 is transmitted to the optical fiber with high efficiency.Moreover, this highly efficient combination is obtained withoutperforming a delicate optical adjustment.

[0220] It is preferable to design the anode 30 and thecore-layer-continuing portion 92 so that the refractive indices differfrom the refractive index of the organic light-emitting layer 40,whereby the light emitted from the organic light-emitting layer 40 isefficiently introduced into the anode 30 and the core-layer-continuingportion 92.

[0221] The action and the effect of the light-emitting device 33000 willbe described below.

[0222] Electrons are introduced from the cathode 50 and holes areinjected from the anode 30 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is partially reflected by the cathode 50 or the EL cladding layer 60.Part of the light is directly introduced into the anode 30 and thecore-layer-continuing portion 92. The light introduced into the anode 30and the core-layer-continuing portion 92 is transmitted inside the ELcore layer 20 toward the edge thereof by distributed feedback typetransmission due to the grating 32 and is emitted to the core layer 90of the optical fiber section 200.

[0223] The embodiment illustrates the case of forming the grating 32 bythe anode 30 and the core-layer-continuing portion 92. The grating 32may be formed by the cathode 50 and the core-layer-continuing portion 92instead of the anode 30 and the core-layer-continuing portion 92 byexchanging the positions of the anode 30 and the cathode 50.

[0224] In the same manner as in the differences between the eleventhembodiment and the twelfth embodiment, almost half of thecore-layer-continuing portion 92 and the cladding-layer-continuingportion 97 which continue respectively from a core layer 90 and acladding layer 95 of an optical fiber section 200 may be removedhorizontally, instead of forming the EL element section 400 inconcentric circles. The anode 30, organic light-emitting layer 40,cathode 50, and EL cladding layer 60 may be laminated almost flat on thesection.

Fourteenth Embodiment

[0225]FIG. 18 is a schematic vertical section of a light-emitting device34000 according to the present embodiment. FIG. 19 is a schematiccross-section viewed along the line H-H in FIG. 18.

[0226] This light-emitting device 34000 differs from the light-emittingdevice 31000 according to the eleventh embodiment in that the EL corelayer 20 comprises the anode 30 and medium layers 46 formed in the anode30 at intervals in the direction of the length. Other features are thesame as in the eleventh embodiment and further description thereof isomitted. Corresponding sections in each figure are indicated by the samesymbols as in the eleventh embodiment.

[0227] In the light-emitting device 34000, the light-transmitting ELcore layer 20 comprises the anode 30 and the medium layers 46 formed inthe anode 30. In the EL core layer 20, the first layer 20 a (part of theanode 30) and the second layer 20 b (medium layers 46) having differentrefractive indices continue alternately to form a grating 42.

[0228] The above-mentioned materials for the optical waveguide can beused as the material for the medium layers 46.

[0229] As shown in FIGS. 18 and 19, the light-emitting device 34000comprises the EL core layer 20 which is formed so as to encircle thecore-layer-continuing portion 92 which continues from the core layer 90of the optical fiber section 200, whereby the light output from the ELcore layer 20 is transmitted to the optical fiber with high efficiency.Moreover, this highly efficient combination is obtained withoutperforming a delicate optical adjustment.

[0230] It is preferable to design the refractive indices of anode 30,medium layers 46, and the core-layer-continuing portion 92 to bedifferent from the refractive index of the organic light-emitting layer40 so that the light emitted from the organic light-emitting layer 40 isefficiently introduced into the anode 30, medium layers 46, andcore-layer-continuing portion 92.

[0231] The action and the effect of the light-emitting device 34000 willbe described below.

[0232] Electrons are introduced from the cathode 50 and holes areinjected from the anode 30 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is partially reflected by the cathode 50 or the EL cladding layer 60.Part of the light is directly introduced into the anode 30 and themedium layers 46. The light introduced into the anode 30 and the mediumlayers 46 is transmitted inside the EL core layer 20 toward the edgethereof by the distributed feedback type transmission due to the grating42 and is emitted to the core layer 90 of the optical fiber section 200.

[0233] This embodiment illustrates the case of forming the grating 42 bythe anode 30 and the medium layers 46 formed at intervals. The grating42 may be formed by the cathode 50 and the medium layers 46 byexchanging the positions of the anode 30 and the cathode 50.

[0234] In the same manner as in the difference between the eleventhembodiment and the twelfth embodiment, almost half of thecore-layer-continuing portion 92 and the cladding-layer-continuingportion 97 which continue respectively from a core layer 90 and acladding layer 95 of an optical fiber section 200 may be removedhorizontally, instead of forming the EL element section 500 inconcentric circles. The anode 30, medium layers 46, organiclight-emitting layer 40, cathode 50, and EL cladding layer 60 may belaminated almost flat on the section.

[0235] According to the above eleventh to fourteenth embodiments, alight-emitting device with a narrow wavelength spectral width, excellentdirectivity, and superior positioning precision between thelight-emission part and transmission part is provided.

[0236] (D) The following fifteenth to twenty-fifth embodimentsillustrate a light-emitting device comprising an organic light-emittinglayer and an optical waveguide having a grating which constitutes aphotonic band gap.

[0237] Among the embodiments described below, the fifteenth toseventeenth embodiments illustrate the case where an organiclight-emitting layer is formed in a defect of a grating.

Fifteenth Embodiment

[0238]FIG. 20 is a cross-sectional view schematically showing alight-emitting device 41000 according to the present embodiment. Thelight-emitting device 41000 comprises a substrate 10, anode 30, holetransport layer 70, organic light-emitting layer 40, cathode 50, andgrating 110.

[0239] The grating 110 comprises a defect 120 and first and secondgratings 110 a and 110 b at each side of the defect 120. These gratings110 a and 110 b can form a photonic band gap to a prescribed wavelengthrange on the basis of the shape (dimensions) and combinations of themedia. First medium layers 130 and second medium layers 140 havingdifferent refractive indices are arranged alternately in the gratings110 a and 110 b. The second medium layer 140 is formed of a holetransport layer 70. The materials for the first medium layers 130 arenot limited insofar as the first medium layers 130 can form a photonicband gap by periodic distribution with the second medium layers 140. Forexample, the second medium layer may be a gaseous body such as air. Inthe case of forming a grating with a so-called air-gap structure by sucha gaseous layer, the difference in the refractive indices of the twomedium layers which constitute a grating can be increased while usingmaterials commonly used for light-emitting devices.

[0240] The organic light-emitting layer 40 is embedded into the defect120. In the present embodiment, the defect 120 of the grating 110 alsofunctions as the light-emitting layer 40. The defect 120 is formed sothat the energy level caused by the vacancy exists inside the emissionspectrum of the organic light-emitting layer 40 by the electricallypumping.

[0241] The cathode 50 is formed locally to cover the surface of theorganic light-emitting layer 40. An electric current is intensivelysupplied to the organic light-emitting layer 40 by forming the cathode50 on only the organic light-emitting layer 40, whereby the electriccurrent loss can be reduced.

[0242] Because the light is confined by the grating 110 having aone-dimensional photonic band gap in the light-emitting device 41000according to this embodiment, optical transmission is controlled only inthe direction in which the grating 110 extends (direction X in FIG. 1).Therefore, light with a leakage mode is transmitted in other directions.In order to control the transmission of the light with such a leakagemode, a cladding layer or a dielectric multiple-layered mirror may beoptionally formed to confine the light. This also applies to thefollowing sixteenth to twenty-fifth embodiments and will not be furthermentioned in the description of these embodiments.

[0243] The action and the effect of the light-emitting device 41000 willbe described below.

[0244] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of these electrons and holes.Light with a wavelength range equivalent to the photonic band gap of thegrating 110 cannot be transmitted inside the grating 110. The excitonsare returned to the ground state at an energy level caused by thevacancy and only the light with a wavelength range equivalent to thisenergy level is emitted. Therefore, light with a remarkably narrowemission spectrum width prescribed by the width of the energy levelcaused by the vacancy can be obtained with high efficiency.

[0245] The function of the photonic band gap also applies to thefollowing sixteenth to twenty-fifth embodiments. Therefore, this willnot be further mentioned in the description of these embodiments.

[0246] As a method of manufacturing the grating 110 of thelight-emitting device 41000 and materials constituting each layer, themethods and materials described above can be appropriately used. Thesemethods and materials also apply to the following other embodiments.

Sixteenth Embodiment

[0247]FIG. 21 is a cross-sectional view schematically showing alight-emitting device 42000 according to the present embodiment. Thelight-emitting device 42000 comprises a substrate 10, anode 30, holetransport layer 70, organic light-emitting layer 40, electron transportlayer 80, cathode 50, and grating 110. The anode 30 and the cathode 50are formed continuously. The hole transport layer 70 and the electrontransport layer 80 are formed discontinuously.

[0248] The grating 110 comprises a defect 120, and the organiclight-emitting layer 40 is formed in this defect 120. First and secondgratings 110 a and 110 b are formed at both sides of the defect 120.These gratings 110 a and 110 b can form a photonic band gap to aprescribed wavelength range. The first medium layers 130 and the secondmedium layer 140 having different refractive indices are arrangedalternately in the gratings 110 a and 110 b. The first medium layers 130are formed from the anode 30 to the cathode 50. The second medium layers140 stand between the hole transport layer 70 and the electron transportlayer 80. Both the first and second medium layers 130 and 140 haveinsulating properties. Because the first and second medium layers 130and 140 have insulating properties, an electric current passes onlythrough the organic light-emitting layer 40 formed in the defect 120through the hole transport layer 40 and the electron transport layer 80when a voltage is applied to the anode 30 and the cathode 50. Thematerials for the first medium layer 130 and the second medium layer 140are limited insofar as these two layers can form a photonic band gap byperiodic distribution.

[0249] The organic light-emitting layer 40 is embedded into the defect120. In the present embodiment, the defect 120 of the grating 110 alsofunctions as the light-emitting layer 40. The defect 120 is formed sothat the energy level caused by the vacancy exists inside the emissionspectrum of the organic light-emitting layer 40 by the electricallypumping.

[0250] The action and the effect of the light-emitting device 42000 willbe described below.

[0251] Electrons are introduced from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of these electrons and holes. Therefore, light with aremarkably narrow emission spectrum width prescribed by the width of theenergy level caused by the vacancy can be obtained with high efficiencyby the photonic band gap of the grating 110.

Seventeenth Embodiment

[0252]FIG. 22 is a cross-sectional view schematically showing alight-emitting device 43000 according to the present embodiment. Thelight-emitting device 43000 resembles the above-described light-emittingdevice 42000 but differs inasmuch as the hole transport layer iscontinuously formed without forming an insulating layer. Thelight-emitting device 43000 comprises a substrate 10, anode 30, holetransport layer 70, organic light-emitting layer 40, cathode 50, andgrating 110. The anode 30, hole transport layer 70, and cathode 50 arecontinuously formed.

[0253] The grating 110 comprises a defect 120, and the organiclight-emitting layer 40 is formed in this defect 120. A first and secondgratings 110 a and 110 b are formed at both sides of the defect 120.These gratings 110 a and 110 b can form a photonic band gap to aprescribed wavelength range. First medium layers 130 and second mediumlayers 140 having different refractive indices are arranged alternatelyin the gratings 110 a and 110 b. The first and second medium layers 130and 140 stand between the hole transport layer 70 and the cathode 50.Both the first and second medium layers 130 and 140 have insulatingproperties. Because the first and second medium layers 130 and 140 haveinsulating properties, an electric current from the cathode 50 passesthrough the organic light-emitting layer 40 formed in the defect 120when a voltage is applied to the anode 30 and the cathode 50. Thematerials for the first medium layer 130 and the second medium layer 140are limited insofar as these two layers can form a photonic band gap bythe periodic distribution.

[0254] The organic light-emitting layer 40 is embedded into the defect120. In the present embodiment, the defect 120 of the grating 110 alsofunctions as the light-emitting layer 40. The defect 120 is formed sothat the energy level caused by the vacancy exists inside the emissionspectrum of the organic light-emitting layer 40 by the electricallypumping.

[0255] The action and the effect of the light-emitting device 43000 willbe described below.

[0256] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of these electrons and holes.Therefore, light with a remarkably narrow emission spectrum widthprescribed by the width of the energy level caused by the vacancy can beobtained with high efficiency by the photonic band gap of the grating110.

[0257] Although an electron transport layer is not formed in thisembodiment, an electron transport layer may be formed between theorganic light-emitting layer 40 and the cathode 50. It is unnecessary toform both the hole transport layer and the electron transport layer.Either of these transport layers may be sufficient. This also applies toother embodiments having a grating constituting a photonic band gap.

Eighteenth Embodiment

[0258]FIG. 23 is a cross-sectional view schematically showing alight-emitting device 44000 according to the present embodiment. Thelight-emitting device 43000 differs from the above-describedlight-emitting devices 41000, 42000, and 43000 inasmuch as the defectand the organic light-emitting layer are formed in the different areas.The light-emitting device 44000 comprises a substrate 10, anode 30, holetransport layer 70, organic light-emitting layer 40, cathode 50, andgrating 110. The anode 30 and the cathode 50 are continuously formed andthe hole transport layer 70 is formed discontinuously.

[0259] The grating 110 comprises a defect 120 and first and secondgratings 110 a and 110 b at each side of the defect 120. These gratings110 a and 110 b can form a photonic band gap to a prescribed wavelengthrange. First medium layers 130 and second medium layers 140 havingdifferent refractive indices are arranged alternately in the gratings110 a and 110 b. The defect 120 and the first medium layers 130 areformed by the hole transport layer 70. The second medium layers 140 haveinsulating properties. The materials for the second medium layers 140are not limited insofar as the second medium layers 140 can form aphotonic band gap by periodic distribution with the first medium layer130 which serves as the hole transport layer 70. The defect 120 isformed so that the energy level caused by the vacancy exists inside theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

[0260] The organic light-emitting layer 40 is formed on the holetransport layer 70 which serves as the defect 120 and stands between thehole transport layer 70 and the cathode 50. In the present embodiment,the defect 120 of the grating 110 is formed in an area different fromthe light-emitting layer 40. Because the defect 120 of the grating 110also serves as the hole transport layer 70 in this embodiment, theorganic light-emitting layer 40 and the defect 120 are formed so thatparts of them are in contact. An insulating layer 90 is formed betweenthe grating 110 and the cathode 50 at each side of the organiclight-emitting layer 40.

[0261] When a voltage is applied to the anode 30 and the cathode 50, anelectric current from the anode 30 and the cathode 50 is concentrated onthe hole transport layer 70, which also serves as the defect 120, andthe organic light-emitting layer 40 by forming the second medium layers140 having insulation properties and the insulating layer 90.

[0262] The action and the effect of the light-emitting device 44000 willbe described below.

[0263] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of these electrons and holes.Therefore, light with a remarkably narrow emission spectrum widthprescribed by the width of the energy level caused by the vacancy can beobtained with high efficiency by the photonic band gap of the grating110.

Nineteenth Embodiment

[0264]FIG. 24 is a cross-sectional view schematically showing a grating110 in a light-emitting device 45000 according to the presentembodiment. This embodiment illustrates a modification of the grating110. The organic light-emitting layer 40 is embedded into only thedefect 120 of the grating 110 in the fifteenth to seventeenthembodiments. In this embodiment, the organic light-emitting layer 40constitutes not only the defect 120 but also part of the medium layersof the grating 110. The second medium layers 140 in the area close tothe defect 120 are formed by filling in the materials for the organiclight-emitting layer 40. The organic light-emitting layer can be formedmore easily by forming the organic light-emitting layer 40 over a widerarea including the defect 120.

[0265] The grating 110 comprises a defect 120 and first and secondgratings 110 a and 110 b at both sides of the defect 120. These gratings110 a and 110 b can form a photonic band gap in a prescribed wavelengthrange. First medium layers 130, second medium layers 140, and thirdmedium layers 150 each having different refractive indices are arrangedalternately in the gratings 110 a and 110 b. The organic light-emittinglayer 40 is formed in the defect 120. The first medium layers 130 andthe second medium layers 140 comprising the organic light-emitting layer40 are arranged alternately near the defect 120, and at both sidesthereof the first medium layers 130 and the third medium layers 150 arearranged alternately. The materials for the first medium layer 130 andthe third medium layer 150 are limited insofar as these at least theselayers can form a photonic band gap by periodic distribution. The defect120 is formed so that the energy level caused by the vacancy existsinside the emission spectrum of the organic light-emitting layer 40 byelectrically pumping.

[0266] The grating 110 shown in FIG. 24 is an example of a grating. Thisgrating can be applied to the light-emitting devices according to thefifteenth to seventeenth embodiments as well as light-emitting deviceshaving other configurations.

[0267] Among the embodiments described below, the twentieth totwenty-third embodiments illustrate the case where an organiclight-emitting layer constitutes a medium layer of a grating.

Twentieth Embodiment

[0268]FIG. 25 is a cross-sectional view schematically showing alight-emitting device 46000 according to the present embodiment. Thelight-emitting device 46000 comprises a substrate 10, anode 30, organiclight-emitting layer 40, cathode 50, and grating 110.

[0269] The grating 110 comprises a defect 120 and first and secondgratings 110 a and 110 b at both sides of the defect 120. These gratings110 a and 110 b can form a photonic band gap to a prescribed wavelengthrange. First medium layers 130 and a second medium layer 140 havingdifferent refractive indices are arranged alternately in the gratings110 a and 110 b. The second medium layer 140 is formed of the organiclight-emitting layer 40. The materials for the first medium layers 130are not limited insofar as the first medium layers 130 can form aphotonic band gap by periodic distribution with the second medium layer140.

[0270] The organic light-emitting layer 40 is embedded into the defect120 and the area where the second medium layers 140 is formed and theupper part thereof are continuous. The defect 120 is formed so that theenergy level caused by the vacancy exists inside the emission spectrumof the organic light-emitting layer 40 by electrically pumping.

[0271] In this embodiment, the organic light-emitting layer 40 functionsas the defect 120 and the second medium layers 140 of the grating 110.These layers can be easily formed by continuously forming the organiclight-emitting layer. This also applies to the following twenty-first totwenty-second embodiments.

[0272] The action and the effect of the light-emitting device 46000 willbe described below.

[0273] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 by applying a prescribed voltage to both the anode 30 and the cathode50. Excitons are formed in the organic light-emitting layer 40 byrecombination of these electrons and holes. Therefore, light with aremarkably narrow emission spectrum width prescribed by the width of theenergy level caused by the vacancy can be obtained with high efficiencyby the photonic band gap of the grating 110.

[0274] In this embodiment, the anode 30 and cathode 50 may be formedonly in the area corresponding the defect 120 formed from the organiclight-emitting layer 40. The efficiency of current injection into thelight-emitting layer 40 can be improved by forming the electrodes insuch a manner. This also applies to other embodiments having a gratingwhich constitutes a photonic band gap.

Twenty-first Embodiment

[0275]FIG. 26 is a cross-sectional view schematically showing alight-emitting device 47000 according to the present embodiment. Thelight-emitting device 47000 comprises a substrate 10, anode 30, holetransport layer 70, organic light-emitting layer 40, electron transportlayer 80, cathode 50, and grating 110. The anode 30 and the cathode 50are continuously formed. The hole transport layer 70 and the electrontransport layer 80 are formed discontinuously.

[0276] The grating 110 comprises a defect 120 and the organiclight-emitting layer 40 is formed in the defect 120. First and secondgratings 110 a and 110 b are formed at both sides of the defect 120.These gratings 110 a and 110 b can form a photonic band gap in aprescribed wavelength range. First medium layers 130 and second mediumlayers 140 each of which have a different refractive index are arrangedalternately in the gratings 110 a and 110 b. The first medium layers 130are formed between the anode 30 and the cathode 50. The second mediumlayers 140 stand between the hole transport layer 70 and the electrontransport layer 80. The first layers 130 has insulating properties.Since the first medium layers 130 has insulating properties, when avoltage is applied to the anode 30 and the cathode 50, an electriccurrent flows efficiently into the organic light-emitting layer 40formed in the defect 120 through the hole transport layer 40 and theelectron transport layer 80. The materials for the first medium layers130 are not limited insofar as the first medium layers 130 can form aphotonic band gap by periodic distribution with the second medium layers140.

[0277] The organic light-emitting layer 40 is embedded into the defect120. Specifically, the defect 120 of the grating 110 also functions asthe light-emitting layer 40 in the present embodiment. The defect 120 isformed so that the energy level caused by the vacancy exists within theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

[0278] The action and the effect of the light-emitting device 47000 willbe described below.

[0279] Electrons are introduced from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of these electrons and holes. Therefore, light with aremarkably narrow emission spectrum width prescribed by the width of theenergy level caused by the vacancy can be obtained with high efficiencyby the photonic band gap of the grating 110.

[0280] The following twenty-second and twenty-third embodimentsillustrate the case where one of the medium layers constituting aphotonic band gap is an organic light-emitting layer and a defect isformed by a layer other than the organic light-emitting layer.

Twenty-second Embodiment

[0281]FIG. 27 is a cross-sectional view schematically showing alight-emitting device 48000 according to the present embodiment. Thelight-emitting device 48000 comprises a substrate 10, anode 30, organiclight-emitting layer 40, electron transport layer 80, cathode 50, andgrating 110. The anode 30, organic light-emitting layer 40, electrontransport layer 80, and cathode 50 are continuously formed.

[0282] The grating 110 comprises a defect 120 and the electron transportlayer 80 is embedded into this defect 120. First and second gratings 110a and 110 b are formed at each side of the defect 120. These gratings110 a and 110 b can form a photonic band gap in a prescribed wavelengthrange. First medium layers 130 and second medium layers 140, each ofwhich have a different refractive index, are arranged alternately in thegratings 110 a and 110 b. The first medium layers 130 are formed fromthe organic light-emitting layer 40. The second medium layers 140 areformed from the electron transport layer 80. The materials for the firstmedium layer 130 and the second medium layer 140 are not limited insofaras these materials can function as the organic light-emitting layer andthe electron transport layer and form a photonic band gap by periodicdistribution of both materials.

[0283] The organic light-emitting layer 40 is formed below the electrontransport layer 80 which serves as the defect 120 and stands between theelectron transport layer 80 and the anode 30. In the present embodiment,the defect 120 of the grating 110 is formed in an area differing fromthe light-emitting layer 40. Since the defect 120 of the grating 110also serves as the electron transport layer 80 in this embodiment, theorganic light-emitting layer 40 and the defect 120 are formed so as tobe in contact in a certain area. The defect 120 is formed so that theenergy level caused by the vacancy exists within the emission spectrumof the organic light-emitting layer 40 by electrically pumping.

[0284] The action and the effect of the light-emitting device 48000 willbe described below.

[0285] Electrons are introduced from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 into theorganic light-emitting layer 40 by applying a prescribed voltage to theanode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of these electrons and holes.Therefore, light with a remarkably narrow emission spectrum widthprescribed by the width of the energy level caused by the vacancy can beobtained with high efficiency by the photonic band gap of the grating110.

Twenty-third Embodiment

[0286]FIG. 28 is a cross-sectional view schematically showing alight-emitting device 49000 according to the present embodiment. Thelight-emitting device 49000 comprises a substrate 10, anode 30, holetransport layer 70, organic light-emitting layer 40, cathode 50, andgrating 110. The anode 30 and the cathode 50 are continuously formed.The hole transport layer 70 and the organic light-emitting layer 40 areformed discontinuously.

[0287] The grating 110 comprises a defect 120 and the defect 120 isformed from the materials which constitute a first medium layer 130.First and second gratings 110 a and 110 b are formed at each side of thedefect 120. These gratings 110 a and 110 b can form a photonic band gapin a prescribed wavelength range. The first medium layers 130 and secondmedium layers 140, each of which have a different refractive index, arearranged alternately in the gratings 110 a and 110 b. The first mediumlayers 130 are formed between the anode 30 and the cathode 50. Thesecond medium layers 140 stand between the hole transport layer 70 andthe cathode 50. The first medium layers 130 have insulating properties.Since the first medium layers 130 have insulating properties, anelectric current is efficiently introduced into only the organiclight-emitting layers 40 which constitute the second medium layers 140through the hole transport layer 70 when a voltage is applied to theanode 30 and the cathode 50. The materials for the first medium layers130 are not limited insofar as the first medium layers 130 can form aphotonic band gap by periodic distribution with the second medium layers140.

[0288] The organic light-emitting layers 40 serve as the second mediumlayers 140 and stand between the hole transport layer 70 and the cathode50. The defect 120 serves as the first medium layer 130. Specifically,the defect 120 of the grating 110 of the present embodiment is formed inan area differing from the light-emitting layer 40. The defect 120 isformed so that the energy level caused by the vacancy exists within theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

[0289] The action and the effect of the light-emitting device 49000 willbe described below.

[0290] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of these electrons and holes.Therefore, light with a remarkably narrow emission spectrum widthprescribed by the width of the energy level caused by the vacancy can beobtained with high efficiency by the photonic band gap of the grating110.

[0291] The following twenty-fourth embodiment illustrates the case wherean organic light-emitting layer is formed by a layer different from agrating.

Twenty-fourth Embodiment

[0292]FIG. 29 is a cross-sectional view schematically showing alight-emitting device 50000 according to the present embodiment. Thelight-emitting device 50000 comprises a substrate 10, anode 30, holetransport layer 70, organic light-emitting layer 40, cathode 50, andgrating 110. The anode 30, organic light-emitting layer 40, and cathode50 are continuously formed. The hole transport layer 70 is formeddiscontinuously.

[0293] The grating 110 comprises a defect 120 and first and secondgratings 110 a and 110 b at each side of the defect 120. These gratings110 a and 110 b can form a photonic band gap in a prescribed wavelengthrange. The first medium layers 130 and second medium layers 140, each ofwhich have a different refractive index, are arranged alternately in thegratings 110 a and 110 b. The defect 120 and the first medium layer 130are formed by the hole transport layer 70. The second medium layer 140has insulating properties. The materials for the second medium layers140 are not limited insofar as the second medium layers 140 can form aphotonic band gap by periodic distribution with the first medium layer130 which serves as the hole transport layer 70. The defect 120 isformed so that the energy level caused by the vacancy exists within theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

[0294] The organic light-emitting layer 40 is formed on the holetransport layer 70 which serves as the defect 120 and stands between thegrating 110 and the cathode 50. Specifically, the defect 120 of thegrating 110 of the present embodiment is formed in an area differingfrom the organic light-emitting layer 40.

[0295] The action and the effect of the light-emitting device 50000 willbe described below.

[0296] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 through the hole transport layer 70 by applying a prescribed voltageto the anode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of these electrons and holes.Therefore, light with a remarkably narrow emission spectrum widthprescribed by the width of the energy level caused by the vacancy can beobtained with high efficiency by the photonic band gap of the grating110.

Twenty-fifth Embodiment

[0297]FIG. 30 is a cross-sectional view schematically showing alight-emitting device 51000 according to the present embodiment. In thelight-emitting device 51000, a grating is formed in the directiondifferent from that in the above-described embodiments. Thelight-emitting device 51000 comprises a substrate 10, anode 30, organiclight-emitting layer 40, cathode 50, and grating 110. The grating 110 isformed perpendicular to the substrate 10.

[0298] The grating 110 comprises a defect 120 and first and secondgratings 110 a and 110 b at each side of the defect 120. These gratings110 a and 110 b can form a photonic band gap in a prescribed wavelengthrange. The first medium layers 130 and second medium layers 140, each ofwhich have a different refractive index, are arranged alternately in thegratings 110 a and 110 b. The first medium layers 130 are formed by theorganic light-emitting layer 40. The materials for the second mediumlayers 140 are not limited insofar as the second medium layers 140 canform a photonic band gap by periodic distribution with the first mediumlayer 130.

[0299] The organic light-emitting layer 40 is embedded into the defect120. Specifically, the defect 120 of the grating 110 also functions asthe light-emitting layer 40 in the present embodiment. The defect 120 isformed so that the energy level caused by the vacancy exists within theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

[0300] The anode 30 and the cathode 50 are formed perpendicular to thesubstrate 10.

[0301] The action and the effect of the light-emitting device 51000 willbe described below.

[0302] Electrons and holes are introduced into the organiclight-emitting layer 40 respectively from the cathode 50 and the anode30 by applying a prescribed voltage to both the anode 30 and the cathode50. Excitons are formed in the organic light-emitting layer 40 byrecombination of these electrons and holes. Therefore, light with aremarkably narrow emission spectrum width prescribed by the width of theenergy level caused by the vacancy can be obtained with high efficiencyby the photonic band gap of the grating 110.

[0303] The present invention is not limited to the above-describedembodiments and many modifications and variations are possible withinthe scope of the present invention.

[0304] For example, some of the above embodiments comprise a pair ofcladding layers. However, if other layers such as the electrode layermade from metals can confine light, the cladding layers may be omitted.Moreover, the above embodiments illustrate light-emitting devicescomprising an organic light-emitting layer as a light-emitting layer. Alight-emitting layer comprising inorganic materials may be used insteadof such an organic light-emitting layer.

[0305] As described above, the present invention can provide alight-emitting device with a narrow spectral width of emissionwavelength and excellent directivity.

1. A light-emitting device comprising: a light-emitting layer beingcapable of emitting light by electroluminescence; a pair of electrodelayers for applying an electric field to the light-emitting layer; andan optical waveguide for transmitting light emitted from thelight-emitting layer, wherein a grating is formed in the opticalwaveguide.
 2. The light-emitting device according to claim 1, wherein:the optical waveguide comprises a core layer mainly transmitting light,and a cladding layer having a refractive index lower than the refractiveindex of the core layer; and the core layer comprises a layer which isdifferent from the light-emitting layer.
 3. The light-emitting deviceaccording to claim 1, wherein: the optical waveguide comprises a corelayer mainly transmitting light, and a cladding layer having arefractive index lower than the refractive index of the core layer; andthe core layer comprises a layer including the light-emitting layer. 4.The light-emitting device according to claim 2 or 3, wherein the gratingis formed in the core layer.
 5. The light-emitting device according toclaim 2 or 3, wherein the grating is formed in a boundary area betweenthe cladding layer and the core layer.
 6. The light-emitting deviceaccording to claim 1, wherein the light-emitting layer constitutes onemedium of the grating and is formed by layers that are discontinuouslyarranged.
 7. The light-emitting device according to claim 6, wherein:the optical waveguide comprises a core layer mainly transmitting light,and a cladding layer having a refractive index lower than the refractiveindex of the core layer; and the grating is formed in the core layer. 8.The light-emitting device according to claim 7, wherein the grating isformed by the light-emitting layer and a hole transport layer.
 9. Thelight-emitting device according to claim 7, wherein the grating isformed by the light-emitting layer and an electron transport layer. 10.The light-emitting device according to claim 7, wherein the grating isformed by the light-emitting layer and an optically transparentelectrode layer.
 11. The light-emitting device according to any one ofclaims 6 to 10, wherein a layer at least made of insulating material isprovided between the pair of electrode layers in the area where thelight-emitting layers are arranged discontinuously.
 12. Thelight-emitting device according to claim 1, further comprising anoptical fiber section formed in one body, wherein the optical fibersection comprises a core layer and a cladding layer, and wherein theoptical waveguide is formed continuously with at least one of the corelayer and the cladding layer of the optical fiber section.
 13. Thelight-emitting device according to claim 12, wherein the opticalwaveguide comprises a core-layer-continuing portion which continues fromthe core layer of the optical fiber section.
 14. The light-emittingdevice according to claim 12 or 13, wherein: the optical waveguidecomprises an EL core layer mainly transmitting light, and an EL claddinglayer having a refractive index lower than the refractive index of theEL core layer; and the EL core layer comprises a core-layer-continuingportion which continues from the core layer of the optical fibersection.
 15. The light-emitting device according to any one of claims 1to 14, wherein the grating is a distributed feedback type grating. 16.The light-emitting device according to claim 15, wherein the grating hasa λ/4 phase shifted structure.
 17. The light-emitting device accordingto claim 15, wherein the grating has a gain-coupled structure.
 18. Thelight-emitting device according to any one of claims 1 to 14, whereinthe grating is a distributed-Bragg-reflection-type grating.
 19. Thelight-emitting device according to claim 1, wherein: the grating has adefect and a one-dimensional periodic refractive index distributionwhich constitutes a photonic band gap; and the defect is designed sothat the energy level caused by the vacancy is within a specificemission spectrum.
 20. The light-emitting device according to claim 19,wherein the light-emitting layer functions as the defect.
 21. Thelight-emitting device according to claim 19, wherein the light-emittinglayer functions as at least part of the defect and the grating.
 22. Thelight-emitting device according to claim 19, wherein the light-emittinglayer is formed in an area different from the defect.
 23. Thelight-emitting device according to any one of claims 1 to 22, whereinthe light-emitting layer comprises organic light-emitting material aslight-emitting material.
 24. A light-emitting device comprising: agrating having a one-dimensional periodic refractive index distributionand constituting a photonic band gap; a defect formed in part of thegrating and is designed so that the energy level caused by the vacancyis within a specific emission spectrum; an organic light-emitting layercapable of emitting light by electrically pumping; and a pair ofelectrode layers for applying an electric field to the organiclight-emitting layer.